Add support for array indices in query params decoding (#542)

* Add support for array indices in query params decoding

* Resolve PR comments

Author: supersonicbyte

Sources/Hummingbird/Codable/URLEncodedForm/URLEncodedFormNode.swift

@@ -7,9 +7,10 @@ enum URLEncodedFormNode: CustomStringConvertible, Equatable {
     /// holds an array of nodes
     case array(Array)
 
-    enum Error: Swift.Error {
+    enum Error: Swift.Error, Equatable {
         case failedToDecode(String? = nil)
         case notSupported
+        case invalidArrayIndex(Int)
     }
 
     /// Initialize node from URL encoded form data
@@ -51,7 +52,7 @@ enum URLEncodedFormNode: CustomStringConvertible, Equatable {
         /// function for create `URLEncodedFormNode` from `KeyParser.Key.Type`
         func createNode(from key: KeyParser.KeyType) -> URLEncodedFormNode {
             switch key {
-            case .array:
+            case .array, .arrayWithIndices:
                 return .array(.init())
             case .map:
                 return .map(.init())
@@ -84,6 +85,11 @@ enum URLEncodedFormNode: CustomStringConvertible, Equatable {
                 // currently don't support arrays and maps inside arrays
                 throw Error.notSupported
             }
+        case (.array(let array), .arrayWithIndices(let index)):
+            guard keys.count == 0, array.values.count == index else {
+                throw Error.invalidArrayIndex(index)
+            }
+            array.values.append(.leaf(value))
         default:
             throw Error.failedToDecode()
         }
@@ -168,7 +174,7 @@ enum URLEncodedFormNode: CustomStringConvertible, Equatable {
 
 /// Parse URL encoded key
 enum KeyParser {
-    enum KeyType: Equatable { case map(Substring), array }
+    enum KeyType: Equatable { case map(Substring), array, arrayWithIndices(Int) }
 
     static func parse(_ key: String) -> [KeyType]? {
         var index = key.startIndex
@@ -186,13 +192,19 @@ enum KeyParser {
             index = key.index(after: index)
             // an open bracket is unexpected
             guard index != key.endIndex else { return nil }
+
             if key[index] == "]" {
                 values.append(.array)
                 index = key.index(after: index)
             } else {
                 // an open bracket is unexpected
                 guard let bracketIndex = key[index...].firstIndex(of: "]") else { return nil }
-                values.append(.map(key[index..<bracketIndex]))
+                // If key can convert to an integer assume it is an array index
+                if let index = Int(key[index..<bracketIndex]) {
+                    values.append(.arrayWithIndices(index))
+                } else {
+                    values.append(.map(key[index..<bracketIndex]))
+                }
                 index = bracketIndex
                 index = key.index(after: index)
             }

Tests/HummingbirdTests/URLEncodedForm/URLDecoderTests.swift

@@ -12,7 +12,7 @@
 //
 //===----------------------------------------------------------------------===//
 
-import Hummingbird
+@testable import Hummingbird
 import XCTest
 
 class URLDecodedFormDecoderTests: XCTestCase {
@@ -79,6 +79,43 @@ class URLDecodedFormDecoderTests: XCTestCase {
         self.testForm(test, query: "b[]=true&b[]=false&i[]=34&i8[]=23&i16[]=9&i32[]=-6872&i64[]=23&u[]=0&u8[]=255&u16[]=7673&u32[]=88222&u64[]=234&f[]=-1.1&d[]=8")
     }
 
+    func testArraysWithIndices() {
+        struct Test: Codable, Equatable {
+            let arr: [Int]
+        }
+        let test = Test(arr: [12, 45, 54, 55, -5, 5])
+        self.testForm(test, query: "arr[0]=12&arr[1]=45&arr[2]=54&arr[3]=55&arr[4]=-5&arr[5]=5")
+
+        let test2 = Test(arr: [12, 45, 54, 55, -5, 5, 9, 33, 0, 9, 4, 33])
+        let query = """
+        arr[0]=12\
+        &arr[1]=45\
+        &arr[2]=54\
+        &arr[3]=55\
+        &arr[4]=-5\
+        &arr[5]=5\
+        &arr[6]=9\
+        &arr[7]=33\
+        &arr[8]=0\
+        &arr[9]=9\
+        &arr[10]=4\
+        &arr[11]=33
+        """
+        self.testForm(test2, query: query)
+    }
+
+    func testArrayWithIndicesThrows() {
+        struct Test: Codable, Equatable {
+            let arr: [Int]
+        }
+        let decoder = URLEncodedFormDecoder()
+        // incorrect indices
+        let query = "arr[0]=2&arr[2]=4"
+        XCTAssertThrowsError(try decoder.decode(Test.self, from: query)) { error in
+            XCTAssertEqual(error as? URLEncodedFormNode.Error, URLEncodedFormNode.Error.invalidArrayIndex(2))
+        }
+    }
+
     func testStringSpecialCharactersDecode() {
         struct Test: Codable, Equatable {
             let a: String

Tests/HummingbirdTests/URLEncodedForm/URLEncodedNodeTests.swift

@@ -46,6 +46,11 @@ class URLEncodedFormNodeTests: XCTestCase {
         XCTAssertEqual(values, [.map("array"), .array])
     }
 
+    func testKeyParserArrayWithIndices() {
+        let values = KeyParser.parse("array[0]")
+        XCTAssertEqual(values, [.map("array"), .arrayWithIndices(0)])
+    }
+
     func testKeyParserMap() {
         let values = KeyParser.parse("array[object]")
         XCTAssertEqual(values, [.map("array"), .map("object")])